This application is based on Application No. 2002-029135, filed in Japan on Feb. 6, 2002, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention generally relates to an engine control apparatus having a mode changeover function for performing diagnosis as to a fail or fault state in the preceding operation of an engine before starting the engine operation. More particularly, the invention is concerned with an engine control apparatus with a mode changeover function which apparatus can be realized in a small size at a low cost with a simplified circuit configuration while ensuring high reliability.
2. Description of Related Art
In general, the engine control apparatus is imparted with a function for checking or diagnosing an engine as to fail or fault and storing the result of the diagnosis so that upon power-up for starting the engine for the succeeding operation, operator or driver can check again the result of the diagnosis by activating a fault diagnosis mode.
For better understanding of the present invention, technical background thereof will be briefly reviewed below. FIG. 4 of the accompanying drawings is a circuit diagram showing schematically and generally a conventional engine control apparatus imparted with a mode changeover function (or fault diagnosis function, to say in another way) known heretofore which is disclosed, for example, in Japanese Patent Application Laid-Open Publication No. 210052/1991 (Japanese Patent No. 2556916).
Referring to FIG. 4, the engine (not shown) is provided with a fault diagnosis input unit 1 for validating the fault diagnosis mode, an overheat input unit 2, an oil-level input unit 3 and an idle input unit 4 which are comprised of input switches responsive to various engine fault or fail state, respectively.
Output terminals of the various input units 1 to 4 mentioned above are connected to input terminals, respectively, of an engine control apparatus 5 which incorporates therein a microcomputer or microprocessor and others. The fault diagnosis input unit 1 is turned on by a driver upon power-up of the engine system, whereby an input signal is inputted to the engine control apparatus 5 as a mode changeover command for validating or activating the fault or fail diagnosis mode.
On the other hand, the other input units 2 to 4 are so designed as to be set to xe2x80x9cONxe2x80x9d state in response to driving signals outputted from various fault detecting units (not shown) upon occurrence of faults or fails in the engine system, whereby the input information indicative of occurrence of the fault is inputted to the engine control apparatus 5.
Connected to the output terminal of the engine control apparatus 5 are a fault diagnosis display device 6 indicating the fault diagnosis mode and an overheat display device 7, an oil-level display device 8 and an idle display device 9 indicating relevant fault states, respectively.
The various display devices 6 to 9 are provided in correspondence to the various input units 1 to 4, respectively. The display devices 6 to 9 are driven by the engine control apparatus 5 in response to the input signals from the corresponding input units to the idle input unit 4, respectively. Further, the display devices 6 to 9 driven by the engine control apparatus 5 serve as external loads of the engine control apparatus.
The fault diagnosis input unit 1 and the fault diagnosis display device 6 are provided separately and independently from an input/output unit(s) designed for the ordinary control purpose. The fault diagnosis input unit 1 is equipped with an switch which can externally be manipulated by a driver or other operator.
Next, description will be made of operation of the conventional engine control apparatus imparted with the mode changeover function shown in FIG. 4.
When the fault diagnosis input unit 1 is turned on upon power-up of the engine system with the engine fault diagnosis signal being inputted, then the engine control apparatus 5 makes decision that the fault diagnosis mode is validated, whereupon the engine control apparatus 5 executes the fault diagnosing operation.
More specifically, the fault diagnosis input unit 1 responds to the turn-on operation to thereby drive the fault diagnosis display device 6. Additionally, when a fault has taken place in the preceding operation, the engine control apparatus 5 drives a corresponding one of the display devices 7 to 9 to thereby display the fault-suffering location in the engine system.
By way of example, when overheat abnormality, oil level abnormality, idle abnormality or the like is stored, corresponding one of the overheat display device 7, the oil-level display device 8 and the idle display device 9 is driven. In this manner, the engine starting operation from the fault or fail state can be evaded.
As is apparent from the above, the conventional engine control apparatus imparted with the mode changeover function is provided with the fault diagnosis input unit 1 for validating the fault diagnosis mode and the fault diagnosis display device 6. Thus, because of the presence of the fault diagnosis input unit 1 and the fault diagnosis display device 6, great difficulty will be encountered in implementing the engine control apparatus imparted with the mode changeover function in a small or miniature size at a low cost.
Furthermore, when a fail event (or fault such as opening, grounding, short-circuiting or the like) should occur in the input switch of the fault diagnosis input unit 1, it becomes impossible to validate or make transition to the fault diagnosis mode or inversely the fault diagnosis mode is fixedly held, making it impossible to restore the ordinary mode from the fault diagnosis mode.
Additionally, when all the input units 2 to 4 are turned on to thereby validate the fault diagnosis mode, there arises a problem that the state in which al the faults have occurred can not discriminatively be identified.
In the light of the state of the art described above, it is an object of the present invention to provide an engine control apparatus imparted with a mode changeover function, which apparatus can be realized in a small size at a low cost by rendering it unnecessary to provide a dedicated fault diagnosis input/output unit while ensuring validation of a fault diagnosis mode as well as a fault decision display without fail.
In view of the above and other objects which will become apparent as the description proceeds, there is provided according to an aspect of the present invention an engine control apparatus imparted with a mode changeover function, which apparatus includes a plurality of input terminals connected to a plurality of input units, respectively, and a plurality of output terminals connected to a plurality of display devices in correspondence to the plurality of input units, respectively. The engine control apparatus is designed to fetch input information from the plurality of input units to thereby drive the plurality of display devices and change over the control mode in response to external input information. The engine control apparatus includes a removable short-circuit line for forming a short-circuit selectively between a predetermined one of the plural output terminals and a predetermined one of the plural input terminals, and a mode changeover decision means for deciding that the control mode changeover state is validated when the short-circuit is formed between the predetermined output terminal and the predetermined input terminal by means of the short-circuit line.
In a preferred mode for carrying out the invention, the mode changeover decision means may be so designed as to execute the steps of outputting a pulse signal of a predetermined period from the predetermined output terminal upon power-up, comparing the input signal from the predetermined input terminal with ON/OFF levels of the pulse signal a predetermined number of times, and deciding that the control mode changeover state is validated when the input signal from the predetermined input terminal is in synchronism with the ON/OFF levels of the pulse signal over the predetermined number of times, while deciding an ordinary state unless the input signal from said predetermined input terminal is in synchronism with the ON/OFF levels of the pulse signal over the predetermined number of times.
With the arrangement of the engine control apparatus, it is possible to validate the fault diagnosis mode and generate a fault decision display without need for providing any dedicated fault diagnosis input/output unit.
The above and other objects, features and attendant advantages of the present invention will more easily be understood by reading the following description of the preferred embodiments thereof taken, only by way of example, in conjunction with the accompanying drawings.